switchtec0: failed to register ntb device: -12 on kernel v5.9+ #95

I git cloned, build and installed Kernel v5.10-rc6 but here the ntb_hw_switchtec driver fails to register:

[    4.081135] switchtec switchtec0: failed to register ntb device: -12

Plus a bunch of

[    0.227914] pci 0000:01:00.1: BAR 2: failed to assign [mem size 0x04000000 64bit pref]

Full dmsg: v5.10-rc6

I experienced the same behaviour on Kernel v5.9 shipped with Ubuntu 20.04.
On the other hand, the same exact setup works flawlessly on Kernel v4.16.

Are there any known issues with Kernel version > 5.9?

HW information

Microsemi PM42100 evaluation kit (Gen4 PFX)

Distro

$ lsb_release -a
No LSB modules are available.
Distributor ID:	Ubuntu
Description:	Ubuntu 20.04.1 LTS
Release:	20.04
Codename:	focal